The research program to be continued through this competing renewal is concerned with the role of the brain nociceptin/orphanin FQ (N/OFQ) opioid neuropeptide system in alcohol addiction. Studies during the previous funding period were dedicated to the treatment target potential of the N/OFQ system for alcohol abuse with emphasis on relapse prevention. The proposed studies are continuous with this work and have two overarching goals. The first is concerned with the behavioral effects of N/OFQ by (a) examining N/OFQ actions on several neurobehavioral effects of ethanol in rats with a history of ethanol (EtOH) dependence (i.e., a state in which neuroadaptive changes exist, including adaptations in the N/OFQ system, that add negative affect as a motivational dimension to EtOH-seeking and reward, and that may modify the behavioral effects of N/OFQ system activation), (b) by establishing the effects of repeated N/OFQ administration to determine whether this treatment enhances the therapeutic efficacy of N/OFQ activation as hypothesized on the basis of the preliminary data or, alternatively, results in tolerance to specific behavioral effects of the peptide, and (c) by comparing the behavioral effects of N/OFQ across lines of rats differing in EtOH preference, Wistar and Marchigian Sardinian Alcohol Preferring rats (msP), the latter carrying an innate dysregulation of the N/OFQ system. The second objective is to elucidate the neurobiological basis of the association between EtOH- induced (history of dependence) or innate (msP rats) alterations in N/OFQ function and EtOH-seeking or reward, as well as to determine whether repeated N/OFQ administration reverses these alterations in N/OFQ function. These objectives will be accomplished in a set of four Specific Aims. Three of these will focus on the effects of acute and repeated N/OFQ treatment on behavioral consequences associated with a history of ethanol dependence. In SPECIFIC AIM 1 the effects of acute and repeated N/OFQ treatment on EtOH self- administration will be established in Wistar and in msP rats with vs. without a history of EtOH dependence. In SPECIFIC AIM 2, animal models of relapse will be utilized to establish the effects of N/OFQ on EtOH-seeking induced by acute footshock stress or EtOH-associated contextual stimuli. In SPECIFIC AIM 3, the effects of N/OFQ on increased anxiety and sensitivity to stress challenges will be examined in two behavioral models of anxiety. Finally, the goal of SPECIFIC AIM 4 is to determine how a history of EtOH dependence alters the function of the N/OFQ system in Wistar compared to msP rats, to identify changes in N/OFQ-NOP neurotransmission produced by repeated N/OFQ treatment in Wistar vs. msP rats, and thereby to shed light on the mechanisms responsible for the inhibitory actions of N/OFQ on EtOH intake, EtOH-seeking, anxiety, and stress reactivity. These studies will be conducted at several levels of analysis including N/OFQ peptide and NOP receptor mRNA expression by in situ hybridization, NOP receptor autoradiography, and measures of the functional status of NOP neurotransmission using [35S]GTP3S binding. The research plan has been developed with the objective of advancing understanding of the treatment target potential of the N/OFQ system, in particular, and of the biological basis of alcohol dependence, in general.